Renping Cao,Jingyi Lin,Bang Lan,Fangrui Cheng,Ting Chen,Lan Li,Ru Liu,Jing Wang
Na 3 Sc 2 (PO 4 ) 3 :R (R = Bi 3+ , Sm 3+ , and Sm 3+ /Bi 3+ ) are successfully synthesized in air atmosphere. The high-temperature solid-state reaction method is used in this work. The X-ray diffractometer patterns confirm that all samples have the single pure phase Na 3 Sc 2 (PO 4 ) 3 . Na 3 Sc 2 (PO 4 ) 3 :Bi 3+ displays blue emission because of the Bi 3+ - Sc 3+ metal-to-metal charge-transfer and the 3 P 1 → 1 S 0 transition of Bi 3+ . Na 3 Sc 2 (PO 4 ) 3 :Sm 3+ shows red-orange emission with four emission bands derived from the 4 G 5/2 → 6 H 5/2 (550 - 582 nm), 6 H 7/2 (582–625 nm), 6 H 9/2 (625–675 nm), and 6 H 11/2 (675–750 nm) transitions of Sm 3+ . The optimal Sm 3+ concentration in Na 3 Sc 2 (PO 4 ) 3 :Sm 3+ is ∼8mol%. An adjustable color emission from blue to red-orange of Na 3 Sc 2 (PO 4 ) 3 :Sm 3+ , Bi 3+ with excitation at 345 nm can be observed when the ratio between Sm 3+ and Bi 3+ ions is changed. Na 3 Sc 2 (PO 4 ) 3 :Sm 3+ , Bi 3+ emits red–orange light under excitation 406 nm. The optimal Bi 3+ concentration in Na 3 Sc 2 (PO 4 ) 3 :8mol%Sm 3+ , Bi 3+ is ∼ 6mol%. The energy transfer from Bi 3+ to Sm 3+ in Na 3 Sc 2 (PO 4 ) 3 :Sm 3+ , Bi 3+ is verified by the spectral properties of samples. We discuss the influences of Bi 3+ or Sm 3+ concentration on luminescence properties of samples and analyze their luminous mechanism by energy level diagram. The experimental results of paper are useful for the research of new Bi 3+ and Sm 3+ doped phosphors.
A series of color-tunable emitting Na3Sc2(PO4)3:Ce3+/Tb3+/Eu3+ (NSPO) phosphors were prepared by a combination of hydrothermal synthesis and low temperature calcination. The phase structure, photoluminescence and energy transfer properties of the samples were studied in detail. The tunable colors were obtained by co-doping the Tb3+ ions into the NSPO:Ce3+ or NSPO:Eu3+ phosphors with varying concentrations. Under UV excitation, the energy transfers from Tb3+ to Eu3+ in the NSPO host occurred mainly via a dipole–dipole mechanism, and the critical distances of the ion pairs (Rc) was calculated to be 17.94 Å by the quenching concentration method. And that, the emission colors of the NSPO:Tb3+,Eu3+ phosphors could be adjusted from green through yellow to red because of the energy transfer from Tb3+ to Eu3+. Based on its good photoluminescence properties and abundant emission colors, the NSPO:Ce3+/Tb3+/Eu3+ phosphors might be promising as potential candidates for solid-state lighting and display fields.
Shihai Miao,Yanjie Liang,Yan Zhang,Dongxun Chen,Shao Yan,Jingwei Liu,Xiao-Jun Wang
Near-infrared (NIR) phosphor-converted light-emitting diodes (LEDs) are becoming an efficient and promising solution for high-power NIR light sources, which have shown a broad range of possible applications in the fields of agriculture, food analysis and biomedical diagnostics. However, there is a long-standing challenge to develop tunable and thermally stable NIR-emitting phosphors as luminescence converters in the design of low-cost, compact and high-efficiency NIR LEDs. Here, we report a tunable broadband NIR photoluminescence in Na3Sc2(PO4)3:Cr3+ phosphors via Ga3+ co-doping and explore their application in NIR LEDs. With the fine-tuning of the doping concentration of Ga3+ ions from 0 to 6%, the NIR luminescence of the obtained phosphor can be tuned from sharp line emission at 694 nm (2E → 4A2 transition of Cr3+) to broadband emission centered at 750 nm (4T2 → 4A2 transition of Cr3+) upon blue light excitation. In the meanwhile, the NIR emission intensity at 100 °C and 150 °C can retain ∼100% and ∼84% of the initial value at room temperature when the Ga3+ content is determined to be 6%, leading to thermally stable broadband NIR emission in the as-synthesized Na3Sc2(PO4)3:Cr3+,Ga3+ phosphors. The NIR LEDs constructed by combining the commercial blue LED chips with the optimized NIR phosphors can generate broadband emission in the wavelength range of 600–1000 nm and deliver ∼4 mW of NIR output power with a power conversion efficiency of 2.6% at a drive current of 60 mA. The potential of the fabricated NIR LEDs as a lighting source for night vision and vein imaging is also demonstrated. The outcomes here highlight promising potential for Na3Sc2(PO4)3:Cr3+,Ga3+ as phosphor-downconverted light emitters in the design of high-power NIR LED devices for practical applications.
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